As for the software, after you've installed the updates, you can install a Language Pack and change the default language. You'll probably want to test that further upgrades retain your chosen default language and doesn't revert back. (I assume that would be the case, but since you won't be physically there to fix it if it isn't, might as well test it first.)

I don't know if the language pack is enough for localizing activities, or if you need to switch your Activity Pack as well.

Finally, if you do get this to work, by all means post in the Tips and Tricks section, as I'm sure other people would be interested about your successes!